The semiconductor industry has experienced rapid growth due to continuous improvements in the integration density of a variety of electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). For the most part, this improvement in integration density has come from repeated reductions in minimum feature size, which allows more components to be integrated into a given area. As the demand for even smaller electronic devices has grown recently, there has grown a need for low resistance structures such as interconnects to further improve the thermal performance of electronic devices.
Semiconductor devices may include a variety of semiconductor structures such as transistors, capacitors, resistors and the like formed on a substrate. One or more conductive layers formed of a metal, metal alloy and the like are separated by dielectric layers. There may be a variety of interconnect structures formed between the conductive layers to interconnect the semiconductor structures, provide an electrical connection between a metal layer and its adjacent metal layer.
Carbon nanotubes have been employed to form low resistance interconnect structures. A carbon nanotube is a tube structure formed of carbon atoms. Carbon nanotubes are of a variety of unique properties such as high strength, high thermal conductivity, good electrical conductivity, good electro-migration and the like. Carbon nanotubes' electronic properties may vary with the differences in their structures. Carbon nanotubes may be of a metallic property or a semiconducting property depending on their physical parameters such as length, diameter and the like.
By selecting appropriate physical parameters such as diameters, carbon nanotubes can be a good conductive material. In particular, despite that a single carbon nanotube may be of a high resistance, a plurality of carbon nanotubes grown in parallel can achieve a resistance as low as copper. As such, carbon nanotubes can be a good material for interconnect structures because they can support high current densities. However, the interconnect structures formed by carbon nanotubes may be of high resistance due to a high resistance contact between the carbon nanotubes and their corresponding metal lines.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale.